Stitch-bonded elastic fabrics are generally known in the art. The elasticity of these fabrics is typically provided by an elastic stitched yarn system, which includes elastomeric yarns, composite yarns made from elastomeric yarns wrapped or tangled with hard yarns, or textured yarns. The stitch-bonded substrate can be a woven, nonwoven or knit fabric or even a film, foil or paper. The yarn system shrinks after stitching by releasing the tension on the elastomeric yarns or by subjecting the elastomeric or textured yarns to heat and moisture. The yarn shrinkage causes the substrate to gather between the stitches. When pulled, the stitch-bonded composite is elastic because the yarns stretch back and the substrate is pulled out flat again. U.S. Pat. Nos. 4,773,238, 4,876,128 and 5,187,952, issued to D. Zafiroglu, among others, describe this technique of building elastic stitched fabrics from fibrous substrate and elastic yarns. A limitation of this technique is that the substrate is buckled out-of-plane between the stitch insertion points, creating a bulky product with a characteristically “bumpy” surface, and in essence stiffening the product, because its thickness increases more than its weight as it gathers.
Another method for forming elastic stitch-bonded products, described in U.S. Pat. No. 4,891,957 issued to Strack, uses a stretched elastomeric fibrous web, stitched under tension. The yarns can be elastic or substantially inelastic. As the substrate shrinks, the yarns may buckle-up, but as the substrate/yarn composite is stretched during use, the yarns take over to reinforce the product. Thus, the yarns supply “strength” and “body,” and the fibrous substrate provides the elasticity to this stitch-bonded fabric. One or more non-elastic fibrous substrates may also be stitched to this elastomeric fibrous web during the stitching process. The elastic fibrous webs used in the '957 patent tend to be expensive, and the buckled yarns and/or added fibrous webs present the same bulk, stiffness and surface unevenness problems as the gathered products using elastic stitching yarns.
Additionally, the requirement of the known fabrics to shrink and gather after stitching increases material and process costs in proportion to the shrinkage ratio, and adds the cost of finishing and heat-setting to the cost of the composite fabric.
Hence, a need exists to produce a stitch-bonded fabric with elastic properties that does not require extensive shrinkage after stitching, remains relatively flat on the surface, and, preferably, utilizes readily available lower-cost components, such as inextensible or non-elastomeric yarns and cast or extruded non-fibrous elastic films or grids.